On Wed, Oct 15, 2014 at 04:06:20PM +0100, Marc Zyngier wrote:
> Commit c387f07e6205 (clocksource: arm_arch_timer: Discard unavailable
> timers correctly) changed the way the driver makes sure both the memory
> and system-register timers have been probed before finalizing the probing.
>
> There is a interesting flaw in this logic that leads to this final step
> never to be executed. Things seems to work pretty well until something
> actually needs the data that is produced during this final stage.
>
> For example, KVM explodes on the first run of a guest when executed on
> a platform that has both memory and sysreg nodes (Juno, for example).
As far as I can tell, the logic is flawed for all cases except two
functional nodes that we manage to probe.
>
> Just fix the damned logic, and enjoy booting VMs again.
>
> Tested on a Juno system.
>
> Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
> Cc: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Reported-by: Riku Voipio <riku.voipio@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
The new logic makes sense to me, so:
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Thanks,
Mark.
> ---
> drivers/clocksource/arm_arch_timer.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index 2133f9d..43005d4 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -660,11 +660,11 @@ static bool __init
> arch_timer_probed(int type, const struct of_device_id *matches)
> {
> struct device_node *dn;
> - bool probed = false;
> + bool probed = true;
>
> dn = of_find_matching_node(NULL, matches);
> - if (dn && of_device_is_available(dn) && (arch_timers_present & type))
> - probed = true;
> + if (dn && of_device_is_available(dn) && !(arch_timers_present & type))
> + probed = false;
> of_node_put(dn);
>
> return probed;
> --
> 2.0.4
>
>
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